Ayhan S. Demir

Enantioselective Synthesis of α-Hydroxy Ketones via Benzaldehyde Lyase-Catalyzed C−C Bond Formation Reaction

(R)-Benzoins and (R)-2-hydroxypropiophenone derivatives are formed on a preparative scale by benzaldehyde lyase (BAL)-catalyzed C−C bond formation from aromatic aldehydes and acetaldehyde in aqueous buffer/DMSO solution with remarkable ease in high chemical yield and high optical purity. The substrate range of this thiamin diphosphate-dependent enzyme was examined with respect to a broad applicability of this benzoin condensation-type reaction in stereoselective synthesis.

Exploring academic procrastination among Turkish students: possible gender differences in prevalence and reasons.

The authors examined the prevalence of and reasons, or excuses, for academic procrastination as a function of gender and academic grade level. In Study 1, a factor analysis of responses by 203 Turkish undergraduate students to an academic procrastination measure provided evidence of reliability and validity for the revised scale. In Study 2, 784 students (363 women, 421 men; M age = 20.6 years, SD age = 1.74 years) completed the validated Turkish Procrastination Assessment Scale-Students. The results were that 52% of students self-reported frequent academic procrastination, with male students reporting more frequent procrastination on academic tasks than female students. Significantly more female students than male students reported greater academic procrastination because of fear of failure and laziness; male students reported more academic procrastination as a result of risk taking and rebellion against control than did female students.

Molecular modifications on carboxylic acid derivatives as potent histone deacetylase inhibitors: Activity and docking studies

In the light of known HDAC inhibitors, 33 carboxylic acid derivatives were tested to understand the structural requirements for HDAC inhibition activity. Several modifications were applied to develop the structure-activity relationships of carboxylic acid HDAC inhibitors. HDAC inhibition activities were investigated in vitro by using HeLa nuclear extract in a fluorimetric assay. Molecular docking was also carried out for the human HDAC8 enzyme in order to predict inhibition activity and the 3D poses of inhibitor-enzyme complexes. Of these compounds, caffeic acid derivatives such as chlorogenic acid and curcumin were found to be highly potent compared to sodium butyrate, which is a well-known HDAC inhibitor.

Asymmetric benzoin reaction catalyzed by benzoylformate decarboxylase

Abstract Aromatic aldehydes are converted into benzoins by benzoylformate decarboxylase catalyzed C–C bond formation. The reaction affords ( R )-benzoins with high enantiomeric excess and in good chemical yields. A broad range of aromatic aldehydes can be used as substrates in aqueous buffer or buffer/DMSO-solutions.

Enantioselective Synthesis of (S)‐2‐Hydroxypropanone Derivatives by Benzoylformate Decarboxylase Catalyzed C−C Bond Formation

Chiral 2-hydroxypropanone derivatives 5a−v, 8a−d, and 10a, b were formed by benzoylformate decarboxylase (BFD) catalyzed C−C bond formation. A donor aldehyde and acetaldehyde as an acceptor were carboligated in aqueous buffer solution with remarkable ease in high chemical yield and good to high optical purity. The substrate range of this thiamin diphosphate dependent enzyme was examined to employ this benzoin condensation type reaction in stereoselective synthesis. The observed dependence of the enantiomeric excess on the substitution pattern could be exploited to design substrates resulting in high selectivity. Best substrates with regard to optical purity were meta-substituted benzaldehyde derivatives. To enable a general and convenient applicability of the BFD-catalyzed C−C bond formation, analytical batch experiments were scaled up to give (S)-2-hydroxy ketones in good to high yields on a preparative scale. Further, the solubility of some of the organic substrates in aqueous solution was increased by the use of cyclodextrin or buffer/DMSO mixtures.

Manganese triacetate mediated regeneration of carbonyl compounds from oximes

Abstract A new method for the direct conversion of oximes into aldehydes and ketones by treatment with manganese triacetate is described. Manganese triacetate can be used for an effective and mild oxidizing agent for the regeneration of carbonyl compounds from oximes in good yield. Many functional groups are tolerated under the reaction conditions.

The Role of Peers and Families in Predicting the Loneliness Level of Adolescents

Abstract The authors investigated the relative contribution of peer relations, family structure, and demographic variables in predicting loneliness in adolescents. Ninth-grade high school students (N = 756) from 8 different schools representing various socioeconomic status in Ankara, Turkey, completed the UCLA Loneliness Scale (D. Russell, L. A. Peplau, & M. L. Ferguson, 1978), the Family Structure Assessing Instrument (A. Gülerce, 1996), and an author-constructed questionnaire involving demographic information and variables on peer relations. Results of multiple regression analyses indicated that all three sets of variables accounted for 41% of the variance in loneliness scores. Additionally, peer relations contributed 34% of the variance, family structure 14%, and demographic variables 3%. Within the limits of the study, peer relations appear to be the best predictors of adolescent loneliness.

Synthesis of 1,2,3,5-tetrasubstituted pyrrole derivatives from 2-(2-bromoallyl)-1,3-dicarbonyl compounds

2-(2-Bromoallyl)-1,3-dicarbonyl compounds are converted into β-enamino, β-hydrazino esters and ketones, followed by base-promoted cyclization, leading to the formation of the corresponding 1,2,3,5-tetrasubstituted pyrroles. 1,2,4- and 1,2,3,4-Substituted pyrroles are also isolated as minor products. Starting from the 2-(2-bromoallyl)-cyclohexane-1,3-dione the corresponding tetrahydro indolone is prepared in good yield.

Oxidation of Aryl Alkyl Ketones To α-Acyloxy, α-(Camphorsulfonyloxy), or α-Hydroxy Derivatives Using Manganese(III) Acetate in Combination with Carboxylic Acids or (1S)-(+)-10-Camphorsulfonic Acid

Abstract The α-oxidation of aryl alkyl ketones using manganese(III) acetate in the presence of various carboxylic acids and (1S)-(+)-10-camphorsulfonic acid provided a convenient synthesis of α-acyloxy, α-(10-camphorsulfonyloxy), and α-hydroxy derivatives in good yield.

Enantioselective synthesis of hydroxy ketones through cleavage and formation of acyloin linkage. Enzymatic kinetic resolution via C–C bond cleavage

Both enantiomers of benzoins and (R)-2-hydroxy-1-phenylpropanone analogues were obtained in high yield on a preparative scale starting from aromatic aldehydes, rac-benzoins and aliphatic aldehydes via enzyme-catalysed C–C bond cleavage and C–C bond formation reactions.